This invention relates to a disk control system for controlling a plurality of disk devices and relates in particular to a method for improving the high speed operation of the disk control system, achieving a lower cost and improving the cost performance.
A diskarray system for controlling a plurality of disk devices is utilized as a storage system in computers. A diskarray system is for instance disclosed in xe2x80x9cA Case for Redundant Arrays of Inexpensive Disks (RAID)xe2x80x9d; In Proc. ACM SIGMOD, June 1988 (Issued by Cal. State Univ. Berkeley). This diskarray operates a plurality of disk systems in parallel and is a technique that achieves high speed operation compared to storage systems utilizing disks as single devices.
A method using the fabric of a fiber channel is a technique for mutually connecting a plurality of hosts with a plurality of diskarray systems. A computer system using this technique is disclosed for instance in xe2x80x9cSerial SCSI Finally Arrives on the Marketxe2x80x9d of Nikkei Electronics, P. 79, Jul. 3, 1995 (No. 639) as shown in FIG. 3. In the computer system disclosed here, a plurality of host computers (hereafter simply called hosts) and a plurality of diskarray systems are respectively connected to a fabric device by way of fiber channels. The fabric device is a switch for the fiber channels and performs transfer path connections between the desired devices. The fabric device is transparent to (or passes) xe2x80x9cframexe2x80x9d transfers which are packets on the fiber channel. The host and diskarray system communicate between two points without recognizing the fabric device.
In diskarray systems of the conventional art, when the number of disk devices were increased in order to increase the storage capacity and achieving a controller having high performance matching the number of disk units was attempted, the internal controller buses were found to have only limited performance and likewise, the processor performing transfer control was also found to have only limited performance. In order to deal with these problems, the internal buses were expanded and the number of processors was increased. However, attempting to solve the problem in this manner made the controller structure more complex due to the control required for a greater number of buses and caused increased overhead and complicated software control due to non-exclusive control of data shared between processors, etc. The rise in cost consequently because extremely high and performance reached its limits so that cost performance was unsatisfactory. Though the cost for this kind could be justified in terms of performance in a large scale system, in systems not on such a large scale the cost did not match performance, expandability was limited and the development period and development costs increased.
The overall system storage capacity and performance can be increased by connecting a plurality of diskarray systems in parallel with a fabric device. However, in this method, there is absolutely no connection between the diskarray systems, and access concentrated on a particular diskarray system cannot be distributed among the other devices so that high performance cannot be achieved in actual operation. Also, the capacity of a logical disk device (hereafter logic unit) as seen from the host is limited to the capacity of one diskarray system so that a high capacity logic unit cannot be achieved.
In an attempt to improve diskarray system reliability, a diskarray system can be comprised of a mirror structure where, in two diskarray systems, the host unit has a mirroring function. However, this method requires overhead due to control required of the mirroring by the host and also has the problem that performance is limited. This method also increases the load that the system administrator must supervise since may diskarray systems are present inside the system. The maintenance costs thus increase since a large number of maintenance personnel must be hired and maintenance fees must be paid for each unit. The plurality of diskarray systems and fabric devices are further all autonomous devices so that the settings must be made by different methods according to the respective device, creating the problem that operating costs increase along with a large increase in operating time and system administrator training time, etc.
In order to resolve these problems with the related art, this invention has the object of providing a disk storage system capable of being structured according to the scale and requirements of the computer system, and a disk storage system that responds easily to needs for high reliability and future expansion.
The disk storage system of this invention contains a storage device having a record medium for holding the data, a plurality of storage sub-systems having a controller for controlling the storage device, a first interface node coupled to a computer using the data stored in the plurality of storage sub-systems, a plurality of second interface nodes connected to any or one of the storage sub-systems, a switching means connecting between a first interface node and a plurality of second interface nodes to perform frame transfer between a first interface node and a plurality of second interface nodes based on one address information added to the frame.
The first interface node preferably has a configuration table to store structural information for the memory storage system and a processing unit to analyze the applicable frame in response to the frame sent from the computer, converts information relating to the transfer destination of that frame based on structural information held in the configuration table, and transfers that frame to the switching means. Further, when transmitting a frame, the first interface node adds the node address information about the node that must receive the frame, to that frame. A second interface node then removes the node address information from the frame that was received, recreates the frame and transfers that frame to the desired storage sub-system.
In the embodiment of this invention, the disk storage system has a managing processor connecting to the switching means. The managing processor sets the structural information in the configuration table of each node according to the operator""s instructions. Information for limiting access from the computer is contained in this structural information.
In another embodiment of this invention, the first interface node replies to the command frame sent from the computer instructing the writing of data, makes copies of that command frame and the following data frames, adds different nodes address information to each frame so the received frame and the copied command frames will be sent to the different respective nodes and sends these frames to the switching means.